Oral contraceptive litigation

United Kingdom

XYZ & Others v Schering Healthcare, Organon and Wyeth
Mackay J: High Court, Queen’s Bench Division – 29 July 2002

This litigation concerned the alleged increased risk of third generation combined oral contraceptive pills (COC3) over second generation combined oral contraceptive pills (COC2) in respect of venous thromboembolic (VTE) injuries such as deep vein thrombosis, pulmonary embolism, and strokes due to paradoxical embolus and venous cerebral thrombosis.

The products concerned were COC3s: Minulet and Tri-Minulet (Wyeth); Femodene (Schering HC), and Mercilon and Marvelon (Organon). These contain oestrogen and a synthetic progestagen, either desogestrel or gestodene. The litigation was a product liability claim brought under the Consumer Protection Act 1987). It was mostly legally aided.

The litigation arose from the “pill scare of October 1995. The UK Committee on the Safety of Medicines published a “Dear Doctor letter to healthcare professionals stating that three unpublished studies indicated “around a twofold increase in risk of VTE associated with COC3 compared with COC2. This had a profound effect on the prescription of such products and, indeed, on the unwanted pregnancy rate. The scientific debate has raged as to whether the difference is real or apparent, due to bias and confounding.

The Court considered the statistical evidence on the determination of causation. It was a preliminary issue in all but name. The issue before the Court was whether the “true relative risk (RR) associated with COC3 of VTE was more than double that associated with COC2. The Court held that if there is a more than doubling of such risk than then more than 50% of women exposed to COC3 who suffered VTE would not have suffered such condition if exposed to COC2 instead of COC3. If medical science cannot identify the women who would have avoided VTE, it “can nevertheless be said of each woman that she was more likely than not to have avoided VTE had she not been exposed to COC3. The Court appeared to be equiparating an aetiological fraction of 50% (RR = 2) with the civil standard of proof of the balance of probabilities.

The Court heard evidence from distinguished epidemiologists and surveyed the epidemiological evidence. The Court favoured the Cox regression analysis which showed no difference in risk. Even if the Court did not rely on this analysis it would have found that the true risk was 1.7, i.e. less than 2.

The importance of this Judgment lies in the approach of the Court to detailed and complex scientific evidence. The Court recognised that it must evaluate and assess such evidence, but that it cannot match or exceed the expertise of the experts assisting the Court. The Court considered also the relationship and interaction between epidemiological evidence and biological mechanistic evidence; this approach is important in all product liability cases where generic causation is in issue. The Court assessed scientific data to determine an essentially scientific question according to legal criteria: this scenario is likely to come before the Courts time and again in medicinal product liability and toxic tort litigation.

For further information please contact Anthony Barton at [email protected] or on +44(0)20 7367 2117.